Study shows Chinese adoptees to have same brain activity as native speakers when exposed to the tones of the language.
Photograph: FREDERIC J. BROWN/AFP

“Lost” first languages leave a permanent mark on the brain, a report this week has found. The study, published in the Proceedings of the National Academy of Sciences (PNAS) in the US, challenges the existing understanding that exposure to a language in the first year of a child’s life can be “erased” if he or she is moved to a different linguistic environment.

The study showed that Chinese children, adopted at 12 months to French-speaking families in Canada, responded to Chinese tones, despite having no conscious understanding of the language.

The experiment involved 49 girls aged between nine and 17 in the Montreal area. The girls fell into three groups: monolingual French speakers with no exposure to Chinese, girls bilingual in French and Chinese, and the Chinese adoptees. All groups were asked to listen to “pseudo words” that used the tones prevalent in Chinese languages. MRI scans revealed that the adoptees showed the same brain activity as native speakers, despite no longer being able to understand and speak anything in the language.

Fred Genesse, professor emeritus at the psychology department at McGill University and co-author of the report, highlighted the significance of the MRI results. He said: “In most people when you process language your left hemisphere is involved. When the monolinguals are listening to these pseudo words, they’re not processing them as language. For them it just sounds like a jumble of sounds. When you look at the two other groups, the areas of the brain they are activating are in the left hemisphere, so they are treating these pseudo words as linguistic units, as words.”

In tonal languages, such as Mandarin, the same word can have many meanings depending on the tone it is spoken in.

David Stringer, associate professor of second-language studies at Indiana University, said the study challenged existing research on the impact early languages have on the brain. “It appears to contradict the findings of similar FMRI studies, which suggested that the childhood language of adoptees may be erased from the brain as the children acquire their new language.”

A 2003 studyobserved Korean children who were adopted by French-speaking families and suggested that early languages were lost.

Alison Mackey, professor of linguistics at Georgetown University, said the new findings provided evidence for the hyphothesis that early language learning is permanent, and what can look like language loss might actually be a problem of retrieval. She said: “It’s there, but it’s not easily accessed, in other words.”

Although the new study was generally well received, Angela Creese, professor of educational linguistics at the University of Birmingham, questioned what was meant by “Chinese” in the study and suggested the results would be strengthened with more detail on the linguistic histories of the babies.

She added that the age of the adoptees (on average 12.8 months) was significant: “It is at that stage that speech starts to emerge in children. The babies would have been able to isolate sounds particular to their language.”

In addition to challenging existing understandings of the impact early languages have on the brain, Kate Watkins, professor of cognitive neuroscience at the University of Oxford, said it had interesting implications for those who may choose to “relearn” their first languages.

“It would suggest that someone who had this very short exposure would have an advantage if they wanted to learn this language again. If your brain is wired up to detect these [sound] categories you are probably going to have an easier time learning the language.”

Mackey questioned whether the Chinese adoptees could get closer to native-like fluency and suggested that follow-up studies could examine the “cognitive benefits” from this early exposure.

“This is a poorly understood, but very exciting area of research,” said Stringer. “We can expect to understand more about the reawakening of dormant language knowledge over the next few years.”